a device that dissipates industrial heat without
dumping it directly into rivers or lakes

In a "wet," natural-draft,
counterflow tower, hot water from the plant is exposed to
air moving up through the chimney-like tower. Heat is
removed by evaporation and the cooled water is emptied
into a waterway or recirculated through the plant. In
cold areas water vapor discharged into the atmosphere can
create a heavy fog.

This Tennessee Valley Authority power
plant on the Green River in Kentucky was, in 1969, the
world's largest coal-fueled electric plant. Its three
wet, natural-draft cooling towers, each 437 feet in
height and 320 feet in diameter at ground level, had a
capacity of 282,000 gallons a minute, which they could
cool through a range of 27.5 degrees.

A "dry" cooling tower (left) avoids
evaporation. The hot water is channeled through tubing
that is exposed to an air flow, and gives up its heat to
the air without evaporating. In this mechanical-draft
version air is moved through the tower by a fan. Dry
towers are costly to operate.

The two five-cell cooling towers seen below were built
by the Marley Company for a chemical plant. They are wet,
mechanical-draft towers of the cross-flow type: a fan in
each stack draws air in through the louvers, across films
of falling water and then up. The towers cool 120,000
gallons a minute through a 20-degree range.